In the related art, there is provided a vehicle equipped with a suspension that includes air springs using compressed air and the like. There is also a vehicle equipped with a vehicle height adjustment apparatus using the air springs. There is a so-called closed type vehicle height adjustment apparatus. This type of vehicle height adjustment apparatus increases a vehicle height by supplying high-pressure air stored in a pressure tank to the air springs that change a suspension state of each wheel. The vehicle height adjustment apparatus decreases the vehicle height by discharging the high-pressure air from the air springs and returning the high-pressure air back to the pressure tank. When a passenger boards a vehicle or loads luggage onto the vehicle, a certain type of vehicle height adjustment apparatus using the air springs may receive an ID code transmitted from a portable device of the passenger, and authenticate the ID code with the vehicle. When the ID code is authenticated, the vehicle height adjustment apparatus decreases the vehicle height so as to facilitate the boarding of the passenger and the loading of the luggage. JP 2006-341665A is an example of the related art.
In the related art, vehicle height is adjusted when a passenger is in a vehicle or is about to board the vehicle. However, the inventor concludes that it is possible to broaden the useable range of the vehicle height adjustment apparatus and improve the added value of the vehicle in a case where the vehicle height adjustment apparatus can be used even when a vehicle is not travelling or a passenger moves away from the vehicle.